recordmydesktop generally works very very well for me. But, when i record some games i've notoced that sound is loosing sync: sounds are later that this what i see. The problem is bigger when resolution in games is high (800x600 is quite ok, bigger are problem). i've also noticed that in such cases recordmydesktop is processing the video file to more than 100% when i stop recording (even 130-140% ;P). i tried to record sound with arecord and video with recordmydesktop -nosound. In such case sound file is a few seconds longer than video.
I guess that recordmydesktop is loosing some frames when it can't grab them fast enough so the video is faster than sound. But is it possible to insert some duplicated frames in place where one is missing ?
i forgot to write that sound is synced at start but keeps loosing it. The more long video is, the more desynchronized sound is at the end ;)
i have some sound issues including that one but these problems were solved by changing the device to pulse or whatever your hardware device is.
if you`re using gtk-recordmydesktop you will find it under the sound tab in the advanced options.just type pulse in the device text box.
i don't use pulseadio neither gtk-recordmydesktop ;)